Entomopathogenic nematode food webs in an ancient, mining pollution gradient in Spain

Assessment of hydrological, geological, and biological parameters of a river basin impacted by old Hg mining in NW Spain

Mercury (Hg) is a toxic metal that can cause adverse effects for the health of ecosystems. The Caudal River is one of the main rivers in the Asturias region (NW Spain), whose basin is highly anthropized, hosting several Hg mines, closed in the last century. Arsenic (As) is also found in the mineral paragenesis of the Hg deposits, posing a greater environmental risk. In the mining sites, remaining old facilities and tailings continue to release these elements into the environment. In this work, samples of fluvial sediments and water were taken, both in areas affected by anthropic activity and in pristine areas, in order to establish the background levels for the critical elements. The mineralogical study of the sediments, combined with EDS microanalysis, is useful to identify mineralogical traps such as Fe oxides or clays to retain the As. The As content in all sampled sediments is above the threshold effect levels (TEL), the possible effect range within which adverse effects occasionally occur, according to the Canadian Sediment Quality Guidelines for the Protection of Aquatic Life. This fact is related to a naturally high geochemical background in the basin, due to the existing mineral deposits. The PEL threshold (the probable effect range within which adverse effects frequently occur) is exceeded by more than an order of magnitude in the sediments downstream of the Hg mines. In these points, the As content in the water, exceeding 700 μg L-1 As, is also above the quality standard established in Spanish legislation. As a result, the Caudal River tributaries in the lower part of the basin do not reach a good ecological state, according to the Hydrological Planning Office, and in some cases their state is deficient, showing low richness and high dominance of macroinvertebrates. Although the concentrations decrease with distance from the source, these findings justify the low ecological quality of the affected watercourses.

Do Old Mining Areas Represent an Environmental Problem and Health Risk? A Critical Discussion through a Particular Case

A bibliographic review was carried out to establish the state of knowledge of a mining area with several centuries of exploitation and currently abandoned. The selected case study, the Sierra Minera de Cartagena-La Union (Spain), has a long history of mining activity, ending in 1990. The area is rich in metallic sulphide (lead, zinc and iron), with underground mines and quarries. The zone is very close to important populations and affects protected sites of special ecological value. It is also adjacent to areas dedicated to agriculture and important centres of tourist interest. It is a territory that meets the requirements to be classified as a critical area, as it is in a state of unstable physical and geochemical equilibrium, giving rise to possible risks to human health and ecosystems. A literature review was carried out according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology criteria, consulting a large number of related publications. The results obtained using the Source-Pathway-Receptor model make it possible to identify the main impacts caused by the contamination sources, the main routes of contamination, as well as the transfer to the biota and the influence on adjacent agricultural soils. In this study, lead, cadmium, zinc, arsenic, copper and manganese were considered as potential toxic elements (PTEs), and data were obtained on concentrations in soil, water and air as well as in fauna and flora. Finally, once the receptors and the associated risks to the ecosystem and human health were identified, a conceptual model of the contamination was drawn up to consider a management proposal to tackle the problems associated with this area, which would also be applicable to critical mining zones.

Optimizing Sampling and Extraction Methods for Plant-Parasitic and Entomopathogenic Nematodes

Plant-parasitic and entomopathogenic nematodes (PPNs and EPNs) are key groups in crop production systems. This study aims at optimizing nematode sampling and extraction methods to benefit integrated pest management (IPM) through (a) management of PPNs and (b) use of EPNs. The impacts of these methods on PPNs and EPNs to achieve cost-effective and efficient IPM programs are presented. The common misuses of sampling and extraction methods are discussed. Professionals engaged in IPM should consider sampling the reliability level in the light of the intended goal, location, crop value, susceptibility, nematode species, and available funds. Logical sampling methodology should be expanded to integrate various factors that can recover extra EPN isolates with differential pathogenicity. It should seek for the best EPN-host matching. Merits of repeated baiting for EPN extraction from soil and sieving for PPN recovery from suspensions are presented. Their extraction values may be modelled to quantify the efficiency of nematode separation. The use of proper indices of dispersion to enhance the biocontrol potential of EPNs or save costs in nematicidal applications is ideally compatible with IPM programs. Selecting an extraction method may sometimes require further tests to find the best extraction method of the existing fauna and/or flora. Cons and pros of modern sampling and extraction techniques are highlighted.

Susceptibility of entomopathogenic nematodes to ivermectin and thiabendazole

The objective of the present study was to determine the susceptibility of entomopathogenic nematodes to ivermectin and thiabendazole. Soil samples collected from the municipalities of Irapuato and León, Guanajuato, Mexico, were obtained, from which the entomopathogenic nematodes (EPNs) of the Steinernematidae and Heterorhabditidae families were isolated. The samples were classified from livestock and nonlivestock soils, and the susceptibility of EPNs to anthelmintics was determined with the larval motility assay (LMA, 24 h) and the larval migration inhibition assay (LMI assay, 48 h). Sterile distilled water (T1) and treatments with 1% ivermectin diluted in 5% DMSO (dimethyl sulfoxide) (T2) and 5% thiabendazole diluted in 5% DMSO (T3) were applied to infective juvenile larvae. Analysis of variance was performed with a factorial design and Tukey's test at 0.05 probability. In addition, different concentrations of ivermectin (0.1, 0.5, 1, 1.2, 1.5, and 2 μg) and thiabendazole (1, 5, 10, 12, 15, and 20 mg) were evaluated to perform a Probit analysis to determine their LC50. All strains of EPNs were susceptible to ivermectin in both the LMA and LMI assay. The results show that EPNs are susceptible to ivermectin and thiabendazole, and the degree depends on the type of test performed, the chemical product used, and the origin of the strain of EPN.

Patterns of Occurrence and Activity of Entomopathogenic Fungi in the Algarve (Portugal) Using Different Isolation Methods

Entomopathogenic fungi (EPF) are distributed in natural and agricultural soils worldwide. To investigate EPF occurrence in different botanical habitats and soil-ecoregions, we surveyed 50 georeferenced localities in the spring of 2016 across the Algarve region (South Portugal). Additionally, we compared three EPF isolation methods: insect baiting in untreated or pre-dried-soil and soil dilution plating on a selective medium. We hypothesized that forest habitats (oak and pine semi-natural areas) and the acidic soil ecoregion may favor EPF occurrence. Overall, EPF species were present in 68% of sites, widely distributed throughout the Algarve. The use of selective media resulted in higher recovery of EPF than did either soil-baiting method. Contrary to our hypothesis, neither vegetation type nor ecoregion appeared to influence EPF occurrence. Traditional and molecular methods confirmed the presence of five EPF species. Beauveria bassiana (34% of sites), was the most frequently detected EPF, using pre-dried soil baiting and soil dilution methods. However, baiting untreated soil recovered Fusarium solani more frequently (26% of sites), demonstrating the utility of using multiple isolation methods. We also found Fusarium oxysporum, Purpureocillium lilacinum and Metarhizium anisopliae in 14%, 8% and 2% of the sites, respectively. Three abiotic variables (pH, soil organic matter and Mg) explained 96% of the variability of the entomopathogen community (EPF and entomopathogenic nematodes) in a canonical correspondence analysis, confirming the congruence of the soil properties that drive the assemblage of both entomopathogens. This study expands the knowledge of EPF distribution in natural and cultivated Mediterranean habitats.

Trace elements concentrations in soil, desert-adapted and non-desert plants in central Iran: Spatial patterns and uncertainty analysis

The concentrations of Cd, Cr and Pb in soil samples and As, Cd, Cr and Pb in plant specimens were analyzed in an arid area in central Iran. Plants were categorized into desert-adapted (Haloxylon ammodendron, Atraphaxis spinosa and Artemisia persica) and non-desert species. It was found that the trace element (TE) accumulating potential of the desert species (Haloxylon ammodendron and Artemisia persica) with a mean value of 0.1 mg kg^-1 for Cd was significantly higher than that of the majority of the non-desert species with an average of 0.05 mg kg^-1. Artemisia also had a high As accumulating capability with a mean level of 0.8 mg kg^-1 in comparison with an average of 0.2 mg kg^-1 for most of the other plant species. The mean values of Cr and Pb in Haloxylon ammodendron and Artemisia persica were 5 and 3 mg kg^-1, respectively. Among the desert-adapted plants, Atraphaxis proved to be a species with high Cr and Pb accumulating potential, as well. The geoaccumulation index and the overall pollution scores indicated that the highest environmental risk was related to Cd. Different statistical analyses were used to study the spatial patterns of soil Cd and their connections with pollution sources. The variogram was estimated using a classical approach (weighted least squares) and was compared with that of the posterior summaries that resulted from the Bayesian technique, which lay within the 95% Bayesian credible quantile intervals (BIC) of posterior parameter distributions. The prediction of cadmium values at un-sampled locations was implemented by multi-Gaussian kriging and sequential Gaussian simulation methods. The prediction maps showed that the region most contaminated by Cd was the north-eastern part of the study area, which was linked to mining activities, while agricultural influence contributed less in this respect.

Wood and bark of Pinus halepensis as archives of heavy metal pollution in the Mediterranean Region

Natural levels of heavy metals (HM) have increased during the industrial era to the point of posing a serious threat to the environment. The use of tree species to record contamination is a well-known practice. The objective of the study was to compare HM levels under different pollution conditions: a) soil pollution due to mining waste; b) atmospheric pollution due to coal-fired power plant emissions. We report significant HM enrichment in Pinus halepensis tissues. Near a burning power plant, Pb content in a tree wood was 2.5-fold higher that in natural areas (no pollution; NP). In mining areas, Cd content was 25-fold higher than NP. The hypothesis that HM contents in tree rings should register pollution is debatable. HM uptake by pines from soil, detoxification mechanisms and resuspended local soil dust is involved in HM contents in wood and bark.